Apparatus and method for auto-negotiation in a communication system

ABSTRACT

A communication system includes a first device and a second device that can advertise multiple capabilities using communication links. A first type of auto-negotiation between the first and second devices is performed using a first communication link between the devices. A second communication link between the devices is used to facilitate a second type of auto-negotiation. For example, the first communication link can include pairs A and B of an IEEE Std. 802.3 four twisted pair cable. The second communication link can include pairs C and D of the cable.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.11/003,739, filed Dec. 6, 2004, now U.S. Pat. No. 7,558,280, claims thebenefit of U.S. Provisional Patent Application No. 60/528,476, filedDec. 11, 2003, each of which is incorporated herein by reference in itsentirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention generally relates to communication systems, andmore specifically to auto-negotiation in a communication system.

2. Background Art

High speed data links transmit data from one location to another overtransmission lines. For example, an Ethernet data link is a well-knownhigh speed data link, and IEEE Std. 802.3 defines an Ethernet standard.

Many Ethernet devices support a protocol handshake method defined byIEEE Std. 802.3 Clause 28, known generally as “auto-negotiation.”Auto-negotiation allows Ethernet (802.3) devices of various capabilitiesto discover each other and to communicate based on a common capability.Each device advertises its own capabilities and matches to theadvertised capabilities of its link partner.

Clause 28 allows communication between some devices advertising aprotocol other than 802.3. For example, devices advertising IEEE Std.802.5 capability or devices advertising IEEE Std. 802.9 capability cancommunicate under Clause 28.

However, Clause 28 does not allow any device to simultaneously advertiseboth the ability to support 802.3 and the ability to support analternate protocol. Clause 28 requires each device to set its SelectorField to either 802.3 or an alternate protocol, but not both.

Moreover, Clause 28 specifies that auto-negotiation occurs over aparticular communication link (e.g., wire pairs A and B) between thedevices. No uses are provided under Clause 28 for other communicationlinks (e.g., wire pairs C and D) between the devices.

Thus, there is a need for a method and apparatus for auto-negotiation ina communication system that allows use of a second communication link tofacilitate auto-negotiation of a second type.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is described with reference to the accompanyingdrawings. In the drawings, like reference numbers indicate identical orfunctionally similar elements. Additionally, the left-most digit(s) of areference number identifies the drawing in which the reference numberfirst appears.

FIG. 1 illustrates IEEE Std. 802.3 Clause 28 auto-negotiation on pairs Aand B of an unshielded twisted pair (UTP) cable having four wire pairs.

FIG. 2 illustrates using pairs C and D of the UTP cable to facilitate anIEEE Std. 1394 auto-negotiation, according to embodiments of the presentinvention.

FIG. 3 illustrates an exemplary protocol hierarchy according to anembodiment of the present invention.

FIG. 4 illustrates exemplary selector field mappings that associateselector fields with particular technologies, according to an embodimentof the present invention.

FIG. 5 illustrates a flow chart of a first method according to anembodiment of the present invention.

FIG. 6 illustrates a flow chart of a second method according to anembodiment of the present invention.

FIG. 7 illustrates a flow chart of a third method according to anembodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Communication systems generally include multiple devices that arephysically or virtually connected via communication links. Acommunication link can include one or more wireless connections, twistedwire pairs, coaxial cables, and/or fiber optic lines, to provide someexamples. Sometimes two devices can be connected by more than one link.For example, a cable including multiple links can connect the twodevices. In another example, the cable itself can be the link.

FIG. 1 shows a first device 110 a and a second device 110 b connected bytwo communication links 120 housed within an unshielded twisted pair(UTP) cable 130. The cable 130 can be category 3, 4, or 5 UTP cable, toprovide some examples. In the embodiment of FIG. 1, each communicationlink 120 of the cable 130 has two twisted pairs. The first communicationlink 120 a includes twisted pairs A and B, and the second communicationlink 120 b includes twisted pairs C and D. The configuration shown inFIG. 1 is commonly used in Ethernet-based communication systems, thoughthe scope of the present invention is not limited in this respect.

“S800T”, also known as IEEE p1394c (e.g., p1394c-200x, draft 0.1, Nov.16, 2003), is a high speed data link that uses a physical layer fromIEEE Std. 802.3 (e.g., IEEE Std. 802.3af-2003), also known as theEthernet standard, to carry IEEE Std. 1394 firewire data. S800T canutilize any suitable cabling standard (e.g., category 5, 5E, or 6),including any future cabling standard (e.g., category 7). S800T canutilize other transmission mediums, such as optical fiber or coaxialcable, to provide some examples. S800T is further described in U.S.Provisional Patent Appl. Nos. 60/441,769, 60/450,357, 60/464,362, and60/484,326, all of which are incorporated herein by reference.Furthermore, the 802.3 Ethernet standard and the IEEE Std. 1394 areincorporated by reference herein in their entirety. IEEE Std. 802.3utilizes four twisted pairs, designated as pairs A, B, C, and D inFIG. 1. According to Clause 28 of IEEE Std. 802.3, auto-negotiationbetween Ethernet devices occurs on pair A (wires 1 and 2) and pair B(wires 3 and 6) only. Thus, in FIG. 1, auto-negotiation between firstand second devices 110 is limited to the first communication link 120 a.The second communication link 120 b, which includes pair C (wires 4 and5) and pair D (wires 7 and 8), is sometimes used for data transmissionafter auto-negotiation is complete. For instance, 1-gigabit or10-gigabit Ethernet can utilize pairs C and D for data transmission.However, IEEE Std. 802.3 does not specify a role for pairs C and D inauto-negotiation, as illustrated in FIG. 1. Thus, the secondcommunication link 120 b traditionally is not used under Clause 28during auto-negotiation.

Referring to FIG. 2, the second communication link 120 b can be used tofacilitate a second auto-negotiation. According to an embodiment, thesecond communication can be used to perform an auto-negotiation of atype that is different than an auto-negotiation that is performed on thefirst communication link 120 a. For instance, if an IEEE Std. 802.3auto-negotiation is performed using pairs A and B, an IEEE Std. 1394auto-negotiation can be performed using pairs C and D. In an embodiment,the second auto-negotiation occurs in parallel with the firstauto-negotiation. For instance, a device 110 can simultaneously performan IEEE Std. 1394 auto-negotiation on pairs C and D and an IEEE Std.802.3 auto-negotiation on pairs A and B.

The first and second devices 110 are capable of advertising theirabilities with respect to multiple technologies. In this example, pairsA and B are used to advertise capabilities for 802.3 operation, andpairs C and D are used to advertise capabilities for the IEEE Std. 1394protocol. Each device 110 can perform the first and secondauto-negotiations in parallel over the first and second communicationlinks 120. Devices 110 that are capable of supporting different and/ormultiple technologies can transfer information over the same cable 130,for example. The first and second auto-negotiations can be performedusing 10-gigabit Ethernet. For instance, the first and secondauto-negotiations can be performed on the same type of twisted paircable.

The second communication link 120 b can provide signal informationoutside of the auto-negotiation protocol. According to an embodiment,the signal information can include instructions to change the advertisedprotocol on the first communication link 120 a or the secondcommunication link 120 b.

For example, if the IEEE Std. 802.3 protocol is advertised on pairs Aand B (i.e. on the first communication link 120 a), the signalinformation can include instructions to stop the 802.3 auto-negotiationon the first communication link 120 a, change the advertised protocol tobe some other protocol (e.g., the IEEE Std. 1394 protocol), and restartauto-negotiation on pairs A and B using the 1394 protocol, rather thanthe 802.3 protocol.

In another example, if the IEEE Std. 1394 protocol is advertised on thesecond communication link 120 b, the signal information can includeinstructions to stop the 1394 auto-negotiation on the secondcommunication link 120 b, change the advertised protocol to be someother protocol (e.g., the IEEE Std. 802.3 protocol), and restartauto-negotiation on pairs C and D using the 802.3 protocol, rather thanthe 1394 protocol.

A media dependent interface (MDI) 210 generally interfaces between adevice 110 and one or more communication links 120. As shown in FIG. 2,the first MDI 210 a interfaces between the first device 110 a and thefirst and second communication links 120. The second MDI 210 binterfaces between the second device 110 b and the first and secondcommunication links 120. For example, the first MDI 210 a or the secondMDI 210 b can be a registered jack-45 (RJ-45) connector. In anembodiment, all eight pinouts of the RJ-45 connector are used during anauto-negotiation operation between the first and second devices 110.

The protocol to be used for data transmission between the first andsecond devices 110, for example, depends on at least one of theadvertised protocols of the first device 110 a matching an advertisedprotocol of the second device 110 b. Referring to FIG. 2, datatransmission between the first and second devices 110 depends on boththe first and second devices 110 advertising at least one of the 802.3and 1394 standards.

In FIG. 2, if both the first and second devices 110 advertise 802.3capability, then the first communication link 120 a produces a match. Ifboth the first and second devices 110 advertise 1394 capability, thenthe second communication link 120 b produces a match.

If only one communication link 120 produces a match, then that matchdefines the protocol to be used for data transmission between the firstand second devices 110. This can be particularly useful when the firstor second device 110 is a legacy device (i.e. a device having 802.3capability) that does not recognize an alternate protocol, such as theIEEE 1394 protocol. Traditional legacy devices generally ignore signalson pairs C and D. Thus, embodiments of the present invention arecompatible with existing 802.3 legacy devices.

Referring to FIG. 2, if only the first communication link 120 a producesa match, then the 802.3 standard is used for communication between thefirst and second devices 110. If only the second communication link 120b produces a match, then the 1394 standard is used. The scope of thepresent invention is not limited to 802.3 and 1394 technologies. Forinstance, the first device 110 a and/or the second device 110 b canadvertise IEEE Std. 802.5 capability or IEEE Std. 802.9 capability, toprovide some examples. Embodiments of the present invention can enable adevice to advertise any suitable capability and to recognize anotherdevice having a matching capability. Devices can advertise 802.3, 802.5,802.9, 1394, or other technologies over the same unshielded twisted pair(UTP) cable, for example. According to an embodiment, the technologiesare advertised over the same 10-gigabit Ethernet. Generally, one of thefirst and second devices 120 advertises a first protocol on the firstcommunication link 120 a, and the other of the first and second devices120 advertises a second protocol on the second communication link 120 b.

If both communication links 120 produce a match, then the protocol to beused for data transmission between the first and second devices 110 istypically determined based on a protocol hierarchy, such as theexemplary protocol hierarchy 300 shown in FIG. 3. The protocol hierarchy300 is often predetermined and can be stored in a memory of the firstdevice 110 a or the second device 100 b, for example. The protocolhierarchy can have any suitable combination of technologies, and eachtechnology can have any suitable priority.

The protocol hierarchy can be a hybrid hierarchy, in which one or moreEthernet technologies and one or more 1394c technologies areintermingled. For example, a first Ethernet technology can have a higherpriority than a 1394c technology, which can have a higher priority thana second Ethernet technology. In another example, a first 1394ctechnology can have a higher priority than an Ethernet technology, whichcan have a higher priority than a second 1394c technology.

Each technology shown in FIG. 3 is associated with a separate priority.However, multiple technologies can share the same priority. Prioritiesare listed from the highest priority of “1” to the lowest priority of“4”, though the protocol hierarchy 300 can include any suitable numberof priorities. In FIG. 3, IEEE Std. 802.3 has the highest priority, andIEEE Std. 1394 has the lowest priority.

For example, if both the first and second devices 110 advertise IEEEStd. 802.3 on the first communication link 120 a and IEEE Std. 1394 onthe second communication link 120 b, then the first and secondcommunication links 120 each produce a match. Referring to the protocolhierarchy 300 of FIG. 3, the IEEE Std. 802.3 protocol has a higherpriority than the IEEE Std. 1394 protocol. The IEEE Std. 802.3 protocolis, therefore, the protocol to be used for data transmission between thefirst and second devices 110. According to an embodiment, a selectorfield can be associated with each device 110 to indicate the protocol tobe advertised by the device 110. FIG. 4 illustrates exemplary selectorfield mappings that associate selector fields 410 with particulartechnologies 420. The selector fields 410 shown in FIG. 4 have five bitseach, though other bit lengths can be used. Referring to FIG. 4,selector field (00001)₂ is associated with IEEE Std. 802.3. Selectorfield (00010)₂ is associated with IEEE Std. 802.9 ISLAN-16T. Selectorfield (00011)₂ is associated with IEEE Std. 802.5. Selector field(00100)₂ is associated with IEEE Std. 1394. Other selector fielddescriptions can be used.

A device 110 that is capable of supporting more than one technology canbe associated with more than one selector field 410. For example, if thefirst device 110 a has an IEEE Std. 802.5 capability and an IEEE Std.802.9 ISLAN-16T capability, the selector fields 410 corresponding tothese technologies can each be associated with the first device 110 a.Referring to the selector field value mappings 400 shown in FIG. 4, theselector fields 410 corresponding to IEEE Std. 802.5 and IEEE Std. 802.9technologies are (00011)₂ and (00010)2, respectively. In this example,the first device 110 a is associated with the (00011)₂ and (00010)₂selector fields 410.

A device 110 generally advertises a particular capability bytransmitting the selector field 410 corresponding to that capability inan encoded stream of data. For example, in a communication system havingtwisted pairs as shown in FIG. 1 and FIG. 2, the selector field 410 canbe transmitted using a series of pulses (i.e. a fast link pulse (FLP)burst) that encode a 16-bit word, commonly referred to as the link codeword (LCW). Selector fields 410 can be transmitted in communicationsystems having other types of communication links (e.g., wirelessconnections, coaxial cables, or fiber optic lines) by using other typesof encoding schemes.

If a device 110 is capable of supporting multiple technologies, then afirst link code word having a first selector field value may betransmitted with a second link code word having a second selector fieldvalue using some type of interleaving. According to an embodiment, thefirst selector field value can be used to advertise 802.3 operation onthe first communication link 120 a, and the second selector field valuecan be used to advertise 1394, or another alternate technology, on thesecond communication link 120 b. In an embodiment, the capabilitiesindicated by the first selector field value and the second selectorfield value can be advertised simultaneously.

According to an embodiment, if a device 110 is capable of supportingmultiple technologies, then the device 110 can transmit the selectorfields 410 corresponding to those technologies in separate LCWs. Forexample, the first capability can be transmitted in a first LCW, and thesecond capability can be transmitted in a second LCW, etc. In accordancewith an embodiment of the present invention, transmitting only oneselector field value 410 can improve compatibility between legacy andnon-legacy devices.

Referring to FIG. 5, a first auto-negotiation of a first type isperformed at block 510 using first and second pairs of conductors. Asecond auto-negotiation of a second type is performed at block 520 usingthird and fourth pairs of conductors. For example, the first, second,third and fourth pairs of conductors can be pairs A, B, C, and D of anIEEE Std. 802.3 four twisted pair cable.

The first and second auto-negotiations can be performed in parallel,rather than in series. Performing the auto-negotiations in parallel canreduce the time required to perform the auto-negotiations. For instance,the first auto-negotiation can require t₁ seconds, and the secondauto-negotiation can require t₂ seconds. If the auto-negotiations areperformed in series, the total time required to perform theauto-negotiations is t₁+t₂ seconds. If the auto-negotiations areperformed in parallel, the total time required to perform theauto-negotiations is t₁ or t₂ seconds, whichever is greater.

In FIG. 6, information relating to a second type of auto-negotiation isprovided at block 610 using the third and fourth pairs of conductors.Based on the information, the first type of auto-negotiation can bestopped, the advertised protocol in a selector field can be changed, andthe second type of auto-negotiation can be started. For instance,changing the advertised protocol can include replacing a protocolassociated with the first type of auto-negotiation with a protocolassociated with the second type of auto-negotiation.

Referring to FIG. 7, a first capability of a first device is advertisedat block 710. A second capability of the first device is advertised atblock 720. For example, the first device can advertise a capability tosupport an IEEE Std. 802.3 protocol and a capability to support an IEEEStd. 1394 protocol. According to an embodiment, advertising the firstand second capabilities is performed in parallel. The first capabilityof a second device is detected at block 730. For example, if the firstcapability is an ability to communicate using the IEEE Std. 802.5standard and the first and second devices both have this capability,then the 802.5 protocol can be used for data transmission between thefirst and second devices.

CONCLUSION

Example embodiments of the methods, systems, and components of thepresent invention have been described herein. As noted elsewhere, theseexample embodiments have been described for illustrative purposes only,and are not limiting. Other embodiments are possible and are covered bythe invention. Such other embodiments will be apparent to personsskilled in the relevant art(s) based on the teachings contained herein.Thus, the breadth and scope of the present invention should not belimited by any of the above-described exemplary embodiments, but shouldbe defined only in accordance with the following claims and theirequivalents.

1. An apparatus for performing auto-negotiation in a communicationssystem, comprising: a first device configured to advertise a firstcapability to operate in accordance with a first communications protocoland to advertise a second capability to operate in accordance with asecond communications protocol, wherein the first device is configuredto perform a first auto-negotiation of the first communications protocolwith a second device when the first capability matches a capability ofthe second device and to perform a second auto-negotiation of the secondcommunications protocol with the second device when the secondcapability matches the capability of the second device, and wherein thefirst device is further configured to use a protocol hierarchy todetermine whether to perform the first auto-negotiation or the secondauto-negotiation when both the first capability and the secondcapability match the capability of the second device.
 2. The apparatusof claim 1, wherein the first device is configured to simultaneouslyadvertise the first capability and the second capability.
 3. Theapparatus of claim 1, wherein the first communications protocol is anInstitute of Electrical and Electronics Engineers (IEEE) Standard 802.3communications protocol, and the second communications protocol is anIEEE Standard 1394 communications protocol.
 4. The apparatus of claim 1,wherein the first communications protocol is an Institute of Electricaland Electronics Engineers (IEEE) Standard 802.3 communications protocol,and the second communications protocol is a non-IEEE Standard 802.3communications protocol.
 5. The apparatus of claim 1, wherein the firstdevice is configured to advertise the first capability over a firstcommunication link and to advertise the second capability over a secondcommunication link.
 6. The apparatus of claim 5, wherein the firstcommunication link and the second communication link each include atleast two pairs of conductors.
 7. The apparatus of claim 1, wherein thesecond device is configured to advertise at least one of a groupconsisting of: the first capability for operation in accordance with thefirst communications protocol, and the second capability for operationin accordance with the second communications protocol.
 8. The apparatusof claim 1, wherein the first communications protocol is assigned ahigher priority than the second communication protocol such that thefirst device is configured to perform the first auto-negotiation whenthe first capability matches the capability of the second device and thesecond capability matches the capability of the second device.
 9. Theapparatus of claim 1, wherein the first communications protocol is anInstitute of Electrical and Electronics Engineers (IEEE) Standard 802.3communications protocol, and the second communications protocol is anIEEE Standard 1394 communications protocol, the IEEE Standard 802.3communications protocol being assigned a higher priority than the IEEEStandard 1394 communications protocol such that the first device isconfigured to perform an auto-negotiation of the IEEE Standard 802.3communications protocol when the first capability matches the capabilityof the second device and the second capability matches the capability ofthe second device.
 10. The apparatus of claim 1, wherein the firstcommunications protocol is an Institute of Electrical and ElectronicsEngineers (IEEE) Standard 802.3 communications protocol, and the secondcommunications protocol is a non-IEEE Standard 802.3 communicationsprotocol, the IEEE Standard 802.3 communications protocol being assigneda higher priority than the non-IEEE Standard 802.3 communicationsprotocol such that the first device is configured to perform anauto-negotiation of the IEEE Standard 802.3 communications protocol whenthe first capability matches the capability of the second device and thesecond capability matches the capability of the second device.
 11. Theapparatus of claim 1, wherein the first device is configured to transmita first link code word having a first selector field to advertise thefirst capability and a second link code word having a second selectorfield to advertise the second capability.
 12. The apparatus of claim 11,wherein the first device is configured to simultaneously transmit thefirst link code word and the second link code word.
 13. A method ofperforming auto-negotiation in a communication system, comprising: (a)advertising, by a first device to a second device, a first capability tooperate in accordance with a first communications protocol; (b)advertising, by the first device to the second device, a secondcapability to operate in accordance with a second communicationsprotocol; and (c) performing, by the first device, a firstauto-negotiation of the first communications protocol with the seconddevice when the first capability matches a capability of the seconddevice or a second auto-negotiation of the second communicationsprotocol with the second device when the first capability matches thecapability of the second device, wherein step (c) comprises: (c)(i)using a protocol hierarchy to determine whether to perform the firstauto-negotiation or the second auto-negotiation when the firstcapability matches the capability of the second device and the secondcapability matches the capability of the second device.
 14. The methodof claim 13, wherein step (b) comprises: (b)(i) simultaneouslyadvertising the first capability and the second capability.
 15. Themethod of claim 13, wherein step (a) comprises: (a)(i) using the firstdevice to advertise the first capability to operate in accordance withan Institute of Electrical and Electronics Engineers (IEEE) Standard802.3 communications protocol, and wherein step (b) comprises: (b) usingthe first device to advertise the second capability to operate inaccordance with an IEEE Standard 1394 communications protocol.
 16. Themethod of claim 13, wherein step (a) comprises: (a)(i) using the firstdevice to advertise the first capability to operate in accordance withan Institute of Electrical and Electronics Engineers (IEEE) Standard802.3 communications protocol, and wherein step (b) comprises: (b) usingthe first device to advertise the second capability to operate inaccordance with a non-IEEE Standard 802.3 communications protocol. 17.The method of claim 13, wherein step (a) comprises: (a)(i) using thefirst device to advertise the first capability over a firstcommunication link, and wherein step (b) comprises: (b) using the firstdevice to advertise the second capability over a second communicationlink.
 18. The method of claim 13, further comprising: (d) using thesecond device to advertise at least one of a group consisting of: thefirst capability, and the second capability.
 19. The method of claim 13,wherein step (c)(i) comprises: (c)(i)(A) assigning the firstcommunications protocol to a higher priority than the secondcommunication protocol; and (c)(i)(B) performing the firstauto-negotiation when the first capability matches the capability of thesecond device and the second capability matches the capability of thesecond device.
 20. The method of claim 13, wherein the firstcommunications protocol is an Institute of Electrical and ElectronicsEngineers (IEEE) Standard 802.3 communications protocol and the secondcommunications protocol is an IEEE Standard 1394 communicationsprotocol, and wherein step (c)(i) comprises: (c)(i)(A) assigning theIEEE Standard 802.3 communications protocol to a higher priority thanthe IEEE Standard 1394 communications protocol; and (c)(i)(B) performingan auto-negotiation of the IEEE Standard 802.3 communications protocolwhen the first capability matches the capability of the second deviceand the second capability matches the capability of the second device.21. The method of claim 13, wherein the first communications protocol isan Institute of Electrical and Electronics Engineers (IEEE) Standard802.3 communications protocol, and the second communications protocol isa non-IEEE Standard 802.3 communications protocol, and wherein step(c)(i) comprises: (c)(i)(A) assigning the IEEE Standard 802.3communications protocol to a higher priority than the non-IEEE Standard802.3 communications protocol; and (c)(i)(B) performing anauto-negotiation of the IEEE Standard 802.3 communications protocol whenthe first capability matches the capability of the second device and thesecond capability matches the capability of the second device.
 22. Themethod of claim 13, wherein step (a) comprises: (a)(i) using the firstdevice to transmit a first link code word having a first selector fieldto advertise the first capability, and wherein step (b) comprises:(b)(i) using the first device to transmit a second link code word havinga second selector field selector field to advertise the secondcapability.
 23. The method of claim 22, wherein step (b)(i) comprises:(b)(i)(A) simultaneously transmitting the first link code word and thesecond link code word.